distensibility of the ascending aorta on magnetic resonance
(MR) and calcification of the vasculature from the ascending
aorta to the iliac arteries(13).
Methods
The Multi-Ethnic Study of Atherosclerosis (MESA) is a multicenter prospective cohort study designed to investigate subclinical cardiovascular disease in individuals without clinical
cardiovascular disease (14). In 2000–2002, MESA recruited
6,814 men and women ages 45– 84 years old from six U.S.
communities: Forsyth County, NC; Northern Manhattan and
the Bronx, N Y; Baltimore City and Baltimore County, MD; St.
Paul, MN; Chicago, IL; and Los Angeles, CA. MESA participants were European-American white, African-American,
Hispanic, or Asian-American (mostly of Chinese origin). Exclusion criteria were clinical cardiovascular disease, weight
> 300 lbs, pregnancy or impediment to long-term partici-
pation(14). MESA protocols and all studies described herein
have been approved by the Institutional Review Boards of all
collaborating institutions.
The MESA Lung Study enrolled 3,965 MESA participants of 4,483 sampled randomly from among those who
consented to genetic analyses, underwent baseline measures
of endothelial function, and attended an examination during the MESA-Lung recruitment period in 2004–2006 (99%,
89%, and 91% of the MESA cohort, respectively). Chinese-Americans were over sampled to improve the precision of estimates for this group. For the current cross-sectional analysis
related to obstructive lung disease, we excluded participants
with restrictive spirometry, defined as a forced vital capacity (FVC) less than the lower limit of normal (LLN)(15) with
a forced expiratory volume in one second (FEV1)/FVC ratio
above 0.70.
Aortic calcification
CT scans of the abdomen were acquired on multidetector
(MD) and electron beam (EBT) scans in 2002 and 2005 in
a randomly selected subset of the cohort. CT images were
analyzed centrally using a standard protocol by the MESA
CT Reading Center. Calcification in the wall of the distal abdominal aorta in an 8 cm in length segment proximal to the
aortic bifurcation was measured. For consistency with previous MESA studies, calcification was identified as a plaque of
≥1mm2 with a density of ≥ 130 Hounsfield units (Hu) and
quantified using the Agatston scoring method(13). Calcification in the proximal abdominal aorta and each iliac artery
was scored similarly.
Similar methods were used on cardiac CT scans in
2000–02(16) to measure ascending aortic calcification and
descending thoracic aortic calcification. Calcification was
identified as plaque of ≥4.6 mm3 and ≥5.5 mm3 on EBT and
MDCT respectively as previously described(17).
Proximal aortic distensibility
Consenting participants underwent a cardiac MR scan in
2000–2002. The protocol, its reliability and characteristics of
MESA participants with and without MR measures have been
previously described (18). All imaging was performed on 1.5
T magnets with a 4-element phased-array surface coil posi-
tioned anteriorly and posteriorly, electrocardiographic gat-
ing, and brachial artery blood pressure monitoring.
Spirometry
Spirometry was conducted in 2004–2006 in accordance with
the American Thoracic Society/European Respiratory Society guidelines (20). All participants performed at least
three acceptable manoeuvres. Tests were conducted using a
dry-rolling-sealed spirometer and software that performed
automated quality checks as manoeuvres were performed
(Occupational Marketing, Inc., Houston, TX). All spirometry exams were reviewed by one investigator and each test
was graded for quality (21). Participants with no acceptable
curves were excluded from spirometry analyses.
CT percent emphysema
Quantitative measures of emphysema on CT scan were performed on the lung fields of full-inspiration cardiac CT scans
acquired in 2000–2002, which imaged approximately 70% of
the lung volume from the carina to the lung bases (22). Two
scans were performed on each participant; the scan with the
higher air volume was used for analyses except in cases of
discordant scan quality, in which case the higher quality scan
was used.
Image attenuation was assessed using modified Pulmonary Analysis Software Suite (23) at a single reading centre
by trained readers without knowledge of other participant information. CT percent emphysema low attenuation area was
defined as the percentage of the total voxels in the lung which
fell below −910 HU. The ICC on blinded re-reads was 0.94.
Attenuation of inside and outside air was measured, and CT
percent emphysema measures corrected for each were obtained for use in sensitivity analyses.
Percent emphysema measures from the carina to lung base
are highly correlated (r = 0.99) with full-lung measures on
the same full-lung scans in smokers. Emphysema measures
from MESA cardiac scans correlated with full-lung scans
(e.g., r = 0.93 on MD-CT scanners) (22).
Potential confounders
Age, gender, race/ethnicity, educational attainment, and
medical history were self-reported. Current smoking was defined as self-report of a cigarette in the last 30 days or urinary cotinine level at the time of CT exam of greater than
